On the size distribution of spots within sunspot groups

Abstract

Size distribution of sunspots provides key information about the generation and emergence processes of the solar magnetic field. Previous studies on the size distribution have primarily focused on either the whole group or individual spot areas. In this paper, we investigate the organization of spot areas within sunspot groups. In particular, we analyze the ratio, $\mathrm{R}$, of the area of the biggest spot (${\mathrm{A}}_{big\_spot}$) inside a group, to the total area of that group (${\mathrm{A}}_{\mathrm{group}}$). We use sunspot observations from Kislovodsk, Pulkovo and Debrecen observatories, together covering solar cycles 17 to 24. We find that at the time when the group area reaches its maximum, the single biggest spot in a group typically occupies about 60% of the group area. For half of all groups, $\mathrm{R}$ lies in the range between roughly 50% and 70%. We also find R to change with the group area, ${\mathrm{A}}_{\mathrm{group}}$, such that $\mathrm{R}$ reaches a maximum of about 0.65 for groups with ${\mathrm{A}}_{\mathrm{group}}\approx 200\mu$Hem and then remains at about 0.6 for lager groups. Our findings imply a scale invariant emergence pattern, providing an observational constraint on the emergence process. Furthermore, extrapolation of our results to larger sunspot groups may have a bearing on the giant unresolved starspot features found in Doppler images of highly active sun-like stars. Our results suggest that such giant features are composed of multiple spots, with the largest spot occupying roughly 55--75% of the total group area (i.e. of the area of the giant starspots seen in Doppler images).

arXiv commentAccepted for publication in Astronomy and Astrophysics

References in corpus (23)

• The Solar Cycle
• Numerical simulations of quiet Sun magnetism: On the contribution from a small-scale dynamo
• The Polarimetric and Helioseismic Imager on Solar Orbiter
• Numerical simulations of active region scale flux emergence: From spot formation to decay
• On-line Tools for Solar Data Compiled at the Debrecen Observatory and their Extensions with the Greenwich Sunspot Data
• Turbulent small-scale dynamo action in solar surface simulations
• On the size distribution of sunspot groups in the Greenwich sunspot record 1874-1976
• Sunspot area catalogue revisited: Daily cross-calibrated areas since 1874
• Comparative analysis of Debrecen sunspot catalogues
• Emergence of magnetic flux generated in a solar convective dynamo. I: Formation of Sunspots and Active regions, and Origin of Their Asymmetries
• Small-Scale and Global Dynamos and the Area and Flux Distributions of Active Regions, Sunspot Groups, and Sunspots: A Multi-Database Study
• Bimodal Distribution of Magnetic Fields and Areas of Sunspots
• Basal magnetic flux and the local solar dynamo
• Spot Sizes on Sun-like Stars
• Forward modelling of brightness variations in Sun-like stars I. Emergence and surface transport of magnetic flux
• On rising magnetic flux tube and formation of sunspots in a deep domain
• Sunspot Sizes and The Solar Cycle: Analysis Using Kodaikanal White-light Digitized Data
• Indirect comparison of Debrecen and Greenwich daily sums of sunspot areas
• Is the small-scale magnetic field correlated with the dynamo cycle?
• Sunspot Group Development in High Resolution
• Loss of toroidal magnetic flux by emergence of bipolar magnetic regions
• Study of the decay rates of the umbral area of sunspot groups by using a high resolution database
• On the Decay of Sunspot Groups and Their Internal Parts in Detail

Cited by in corpus (4)

• Scrutinizing the relationship between plage areas and sunspot areas and numbers
• SAGE: A tool to constrain impacts of stellar activity on transmission spectroscopy
• How rare are counter Evershed flows?
• Analytic model for photometric variation due to starspots on a differentially rotating star